Polymer blends which have a combination of both thermoplastic and elastic properties are generally obtained by combining a thermoplastic with an elastomeric composition in a way such that the elastomer is intimately and uniformly dispersed as a discrete particulate phase within a continuous phase of the thermoplastic. Early work with vulcanized compositions is found in U.S. Pat. No. 3,037,954 which discloses static vulcanization as well as a technique of dynamic vulcanization wherein a vulcanizable elastomer is dispersed in a resinous thermoplastic polymer. The elastomer is cured while continuously mixing and shearing the polymer blend. The resulting composition is a micro-gel dispersion of cured elastomer, such as butyl rubber, chlorinated butyl rubber, polybutadiene or polyisobutene in an uncured matrix of thermoplastic polymers such as polypropylene.
U.S. Pat. No. 5,003,003 is directed to blends of polyamide resin with elastomeric ethylene-propylene polymers which have been functionalized, then crosslinked after dispersion in the polyamide resin. The resulting blend has improved tensile strength, elongation and oil resistance.
U.S. Pat. No. 5,238,990 discloses a thermoplastic blend of polyamide with a grafted polymer which is a reaction product of: a) copolymers or halogen containing copolymers of a C.sub.4-7 isomonoolefin and an alkylstyrene, and b) an unsaturated carboxylic acid or a derivative thereof. The blend is said to have improved impact strength while maintaining the high flexural modulus of the polyamide.
In U.S. Pat. No. 5,244,961, a process is described for the preparation of a blend of thermoplastic polyamide halogen containing copolymers of C.sub.4-7 isomonoolefin and para-alkylstyrene, in the presence of a metal compound. The blend has improved low impact resistance at low temperatures.
PCT Published Application WO 95/26380 describes a process for producing a thermoplastic elastomer having improved service properties which incorporates copolymers of a functionalized polyolefin and a polyamide in a thermoplastic elastomer selected from: a) a thermoplastic polyolefinic copolymers, and a olefinic rubber which is fully crosslinked, partially crosslinked or not crosslinked, and optional additives; b) a block copolymers of styrene/conjugated diene/styrene and/or its hydrogenated derivative, optionally compounded with a thermoplastic polyolefinic homopolymer or copolymers and/or common additives; and c) any blend of a and b.
U.S. Pat. No. 4,594,390 describes a process for the preparation of thermoplastic elastomers comprising a blend of plastic and cured rubber by dynamic vulcanization wherein the blend is subjected to high shear in a mixer such as fully intermeshing and co-rotating twin screw extruder. All of the plastic and rubber and the other compounding ingredients, except a cure activator, are fed into the entry port of the extruder. In the first one third of the extruder, the composition is masticated to melt the plastic into an essentially homogenous blend. The cure activator is added to an entry port located about one-third of the length from the initial entry port. The last two-thirds of the extruder is regarded as a dynamic vulcanization zone.
U.S. Pat. No. 5,574,105 describes a thermoplastic elastomer comprising a tri-blend of engineering resin, dynamically vulcanized alloy of thermoplastic olefinic polymer and elastomeric copolymers, in the presence of a compatabilizer for the engineering resin and dynamically vulcanized alloy. The compositions retain their structural integrity at high temperatures and have good tensile elongation and fluid resistance properties.